Question: $-\dfrac{9}{4} + \dfrac{1}{10} = {?}$
Explanation: $ = - {\dfrac{9 \times 5}{4 \times 5}} + {\dfrac{1 \times 2}{10 \times 2}} $ $ = - {\dfrac{45}{20}} + {\dfrac{2}{20}} $ $ = - \dfrac{{45} + {2}}{20} $ $ = -\dfrac{43}{20}$